Hello everyone,

There is an issue with the chrooted builds on Hurd. In
nix/libstore/build.cc CHROOT_ENABLED
is false because HAVE_UNSHARE && HAVE_SYS_MOUNT_H are not defined on Hurd.

The part that we are interested from build.cc is at line 1768. The
part of the code in that if, is used by the daemon for chrooted
builds. At this specific part of the daemon we only need
 HAVE_CHROOT to be defined, which is true on hurd, for the builds to
work. With this workaround,
things seem to work for me until now. WDYT?

I am sending this patch in order to discuss what could be done and see
if anyone has any better ideas.

Manolis